Electro-optic liquid sensor enabling in-liquid testing

ABSTRACT

An electro-optic liquid sensor may include a light source, a light detector, a prism, and a reflective optical member. The optical member may be arranged to reflect light emitted by the light source to the light detector when a liquid is disposed between the light source and the optical member. The electro-optic sensor may enable assessment of its operational state in the presence of liquid, thus improving on known electro-optic liquid sensors. A method of operating a sensor to assess the presence of liquid is disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Ser. No. 14/912,747, filed Feb.18, 2016, which is a National Phase Application of PCT/2014/054696,filed Sep. 9, 2014, which claims the benefit of U.S. Provisional PatentApplication No. 61/875,892, filed Sep. 10, 2013, the foregoing beinghereby incorporated by reference as though fully set forth herein.

TECHNICAL FIELD

The present disclosure relates generally to liquid sensors, includingelectro-optic liquid sensors.

Numerous components in numerous different fields are dependent on thepresence or absence of liquid, or a certain amount of liquid.Accordingly, sensors have been developed for detecting the presence offluid. One known sensor type is an electro-optic sensor including alight source, a prism, and a light detector.

SUMMARY

The present disclosure relates generally to liquid sensors, includingelectro-optic liquid sensors.

Numerous components in numerous different fields are dependent on thepresence or absence of liquid, or a certain amount of liquid.Accordingly, sensors have been developed for detecting the presence offluid. One known sensor type is an electro-optic sensor including alight source, a prism, and a light detector.

In known electro-optic liquid sensors, light emitted from the lightsource may be returned to the light detector by the prism only if noliquid is present. If liquid is present, no light may be returned to thelight detector.

An embodiment of an electro-optic liquid sensor may include a lightsource, an light detector, a prism, and a reflective optical member(which may also be referred to as an optical shield). The optical membermay be arranged so as to reflect light emitted by the light source tothe light detector when a liquid is disposed between the light sourceand the optical member.

Liquid sensors according to the present disclosure may improve on knownelectro-optic liquid sensors by providing capability for assessing theoperational state of the sensor in the presence of liquid. In contrast,known electro-optic sensors are generally only capable of being testedwhile not in liquid. Accordingly, electro-optic sensors according to thepresent disclosure may enable improved testing and functionality overknown electro-optic liquid sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram view of an exemplary embodiment of a systemincluding a component for which determining the presence of fluid may bedesirable.

FIG. 2 is a diagrammatic view of an exemplary embodiment of anelectro-optic liquid sensor.

FIG. 3 is a diagrammatic view of the electro-optic liquid sensor of FIG.2 illustrating the operation of the liquid sensor in the absence ofliquid.

FIG. 4 is a diagrammatic view of the electro-optic liquid sensor of FIG.2 illustrating the operation of the liquid sensor in the presence ofliquid.

FIG. 5 is a flow chart illustrating an embodiment of a method ofoperating an electro-optic liquid sensor.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentdisclosure, examples of which are described herein and illustrated inthe accompanying drawings. While the invention will be described inconjunction with embodiments, it will be understood that they are notintended to limit the invention to these embodiments. On the contrary,the invention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims.

Referring to the figures, in which like reference numerals refer to thesame or similar features in the various views, FIG. 1 is a block diagramview of a system 10 including a component 12 for which determining thepresence of liquid may be desirable. The component 12 may include aliquid chamber 14, and the system 10 may further include a liquid sensor16 and an electronic control unit (ECU) 18.

The component 12 may be any component in any field that includes or maybe exposed to liquid in its operation. For example, the component 12 maybe or may be included in a mechanical, electrical, hydraulic, pneumatic,or other known actuator or actuation system. The component 12 mayinclude a liquid chamber 14 configured to store or receive a liquid. Theliquid may be, for example only, of a type necessary for thefunctionality of the component 12 (e.g., hydraulic fluid, liquid forlubrication, fuel, etc.), liquid incidental to the environment of thecomponent 12, and/or liquid that is detrimental to the function of thecomponent 12.

The liquid sensor 16 may be coupled with the component 12. For example,the liquid sensor 16 may be disposed within the liquid chamber 14 of thecomponent 12. The liquid sensor 16 may be an electro-optic sensoraccording to the present disclosure, such as that described inconjunction with FIGS. 2-4.

With continued reference to FIG. 1, the ECU 18 may be electricallycoupled to the sensor 16 and may be configured to drive the sensor 16,receive feedback from the sensor 16, assess whether liquid is present orabsent in the liquid chamber 14, and/or assess the operational state ofthe sensor 16. The ECU 18 may comprise, in embodiments, one or more of aprocessor, a non-volatile computer-readable memory, anapplication-specific integrated circuit (ASIC), field-programmable gatearray (FPGA), and/or other known processing or memory device. The ECU 18may be or may comprise a dedicated processing resource for the sensor16, or may be or may comprise processing resources for numerous sensors,components, and/or systems. The ECU 18 may be electrically coupled tothe sensor 16 through known wired and/or wireless connections.

FIG. 2 is a diagrammatic view of an exemplary embodiment of theelectro-optic liquid sensor 16. The sensor 16 may include a light source20, a light detector 22, a prism 24, and a reflective optical member 26(which may also be referred to as an optical shield), which may begenerally disposed within a housing 28. The housing may include one ormore liquid ports 30 for permitting liquid to flow into and out of achamber 32 of the housing 28. The chamber 32 may define a gap betweenthe prism 24 and the optical member 26 of a size d. In an embodiment, dmay be about an inch or less. Of course, other dimensions may beemployed as appropriate for particular applications.

The light source 20 may be configured to emit light of a chosenfrequency and power (or powers) appropriate for a given application(i.e., appropriate for the characteristics of the other elements of thesensor, such as shape, orientation, materials, reflectivity, etc.,and/or according to characteristics of the liquid to be detected, suchas density, scattering properties, etc.). As used herein, a lightfrequency should be understood to include either or both of a specificfrequency of light and a frequency band. In an embodiment, the lightsource 20 may be configured to emit light in the infrared portion and/orthe near-infrared portion of the electromagnetic spectrum. The lightsource 20 may be or may include one or more of a light-emitting diode(LED), a laser, or other known light source, in an embodiment.

The light detector 22 may be configured, in an embodiment, to detectlight of one or more frequencies of light, including at least thefrequency of light emitted by the light source 20. The light detector 22may be or may include one or more of a phototransistor, photodiode,and/or other known light detecting device.

The prism 24 may be a member, article, or device comprising one or morecomponents configured in size, shape, and materials to reflect a lightsignal from the light source 20 to the light detector 22 in certainconditions and to pass light from the light source 20 through the prism24 in certain conditions. For example only, the prism may be configuredto reflect light from the light source 20 to the light detector 22 whenliquid is not present around the prism 24, and to pass light from thelight source through the prism 24 when liquid is present around theprism 24. In an embodiment, for example only, the prism 24 may compriseborosilicate glass, fused silica (quartz), one or more polymers, etc,that is optically transmissive at least to light of the frequencyemitted by the light source 20. Thus, in an embodiment, the prism 24 maybe optically-transmissive to light in the infrared and/or near-infraredportions of the electromagnetic spectrum, for example only.

The reflective optical member 26 may be arranged and configured toreflect light emitted by the light source 20 to the light detector 22,in certain conditions. The optical member 26 may have a degree ofreflectivity for one or more frequencies of light that is tailored for aparticular application. In certain embodiments, the optical member 26may have complete or near-complete reflectivity for the frequency oflight emitted by the light source 20. In other embodiments, the opticalmember 26 may have less-than-complete reflectivity for the frequency oflight emitted by the light source 20.

The reflective optical member 26 may be disposed, in an embodiment, on aside of the housing 28 opposite the light source 20 and the lightdetector 22. The light source 20 may emit light in the direction of theoptical member 26. The prism 24 may be disposed between the light source20 and the optical member 26, in an embodiment, and between the lightdetector 22 and the optical member 26, in an embodiment. Accordingly, inthe embodiment generally illustrated in FIG. 2, light may travel fromthe light source 20, through the prism 24, through the chamber 32, tothe optical member 26, and be reflected by the optical member 26 backthrough the chamber 32 and prism 24 to the light detector 22, in certainconditions. The distance d between the optical member 26 and the prism24 may be tailored to the geometric relationship between the opticalmember 26, prism 24, light detector 22, and light source 20, in anembodiment, for the optical member 26 to effectively reflect lightemitted by the light source 20 to be returned to the light detector 22.

The electro-optic liquid sensor 16 may be configured to detect thepresence of liquid by returning a different amount of light from thelight source 20 to the light detector 22 when liquid is present in thechamber 32 than when liquid is not present in the chamber 32. Forexample, as shown in FIG. 3, when no liquid is present in the chamber32, and the chamber 32 is filled with air, the prism 24 may return afirst amount of light from the light source 20 to the light detector 22.In an embodiment, the prism 24 may return substantially all lightemitted by the light source 20 to the light detector 22 when no liquidis present. In contrast, as shown in FIG. 4, when the chamber 32 isfilled with liquid, the prism 24 may return very little of or none ofthe light from the light source 20 to the light detector 22. The prism24 may pass some portion of the light emitted by the light source 20,some of which light may disperse in the liquid, and some of which lightmay propagate to the optical member 26, be reflected by the opticalmember 26 to the light detector 22, and be received by the lightdetector 22. Accordingly, a relatively higher amount of light receivedby the light detector 22 may be associated with the absence of liquidfrom the chamber 32, and a relatively smaller amount of light receivedby the light detector 22 may be associated with the presence of liquidin the chamber 32.

The electro-optic liquid sensor 16 may improve on known electro-opticsensors by enabling the sensor 16 to be tested in the presence ofliquid. Known electro-optic sensors generally do not provide any meansby which a light signal may be returned to the light detector in thepresence of liquid. As a result, a faulty sensor may beindistinguishable from the presence of liquid in known sensors. Incontrast, because the electro-optic sensor 16 of the present disclosuremay return a light signal to the light detector 22 in the presence ofliquid, a faulty sensor (which may indicate zero light received by thelight detector 22) may be distinguished from the presence of fluid(which may indicate a nonzero amount of light received by the lightdetector, but less light received by the light detector 22 than whenliquid is absent).

Although embodiments of the electro-optic liquid sensor 16 are describedherein with respect to particular materials, shapes, dimensions, lightcharacteristics, etc., it should be understood that such details areexemplary only and are not limiting except as explicitly recited in theclaims. Numerous modifications and alterations may be made within thespirit and scope of the present disclosure.

Referring to FIGS. 1 and 2, the ECU 18 may be configured to operate theelectro-optic sensor 16 to determine whether liquid is present in thechamber 32 and to determine whether the sensor 16 is or is not operatingproperly (i.e., assess the operational state of the sensor 16).Accordingly, in an embodiment, the ECU 18 may be configured to operatethe sensor 16 in a liquid detection mode and a test mode. The liquiddetection mode and the test mode may be implemented separately by theECU, or may be implemented together.

FIG. 5 is a flow chart generally illustrating a method 40 of operatingan electro-optic sensor 16. One or more steps of the method 40 may beperformed by the ECU 18 shown in FIG. 1 to operate the sensor 16 of FIG.2. The method 40 may include steps for implementing a liquid detectionmode and a test mode of the electro-optic sensor together.

Referring to FIGS. 2 and 5, an embodiment of a method 40 may begin witha first driving step 42 that includes driving the light source 20 at afirst frequency and intensity. The frequency and intensity may beselected according to the characteristics of the components of thesensor 16 and according to the liquid to be detected. The method 40 maycontinue to a first receiving step 44 that includes receiving reflectedlight with the light detector 22. The received light may be of the samefrequency as that emitted by the light source 20 in the first drivingstep 42. In a first comparison step 46, the amount or intensity or lightreceived, R₁, may be compared to a first threshold, T₁.

If the amount or intensity of light detected in the first receiving step44 is less than the first threshold T₁, the method 40 may continue to asecond driving step 48 that includes driving the light source 20 at asecond frequency and intensity. The second frequency may be the same asthe first frequency, in an embodiment. The second intensity may be thesame as the first intensity, in an embodiment. In another embodiment,the second frequency and/or intensity may be different from the firstfrequency and/or intensity. For example only, the second intensity maybe higher than the first, in an embodiment. A higher intensity may beused in the second driving step 48 than in the first driving step 42 toensure that, if liquid is present, the light will have sufficient energyto propagate through the liquid from the light source 20 to the opticalmember 26 and back to the light detector 22. Thus, as in the firstdriving step 42, the frequency and intensity of light in the seconddriving step 48 may be selected according to the type of liquid to bedetected and the characteristics of the elements of the sensor.

The method 40 may continue to a second receiving step 50 that includesreceiving reflected light with the light detector 22. The received lightmay be of the same frequency as that emitted by the light source 20 inthe second driving step 48. In a second comparison step 52, the amountor intensity or light received, R₂, may be compared to a secondthreshold, T₂. If the amount or intensity of light received is greaterthan the second threshold (i.e., if R₂>T₂), it may be concluded at afirst conclusion step 54 that liquid is present and that the sensor 16is functioning properly. If the amount or intensity of light received R₂is not greater than the second threshold T₂, it may be concluded at asecond conclusion step 56 that the sensor 16 is not functioningproperly.

In the first comparison step 46, if the amount or intensity of lightreceived is greater than the first threshold (i.e., if R₁>T₁), themethod 40 may advance to a third driving step 58 that includes drivingthe light source 20 at a third frequency and intensity. The thirdfrequency may be the same as either or both of the first frequency andthe second frequency, in an embodiment. The third intensity may be thesame as either or both of the first intensity and the second intensity,in an embodiment. In another embodiment, the third frequency and/orintensity may be different from either or both of the first and secondfrequency and/or intensity. The frequency and intensity of light in thethird driving step 58 may be selected according to the type of liquid tobe detected and the characteristics of the elements of the sensor.

The method 40 may continue to a third receiving step 60 that includesreceiving reflected light with the light detector 22. The received lightmay be of the same frequency as that emitted by the light source 20 inthe third driving step 58. In a third comparison step 62, the amount orintensity or light received, R₃, may be compared to a third threshold,T₃. The third threshold T₃ may be set to an amount or intensity of lightthat is higher than a properly-functioning sensor could detect given theamount or intensity of light emitted in the third driving step 58. Ifthe amount or intensity of light received is less than the thirdthreshold, it may be concluded at a third conclusion step 64 that noliquid is present and that the sensor 16 is functioning properly. If theamount or intensity of light received R₃ is greater than the thirdthreshold T₃, it may be concluded again at the second conclusion step 56that the sensor 16 is not functioning properly.

The thresholds T₁, T₂, T₃ for determining whether liquid is present andwhether the sensor 16 is functioning properly may be selected accordingto the characteristics of the liquid to be detected and thecharacteristics of the elements of the sensor 16, in an embodiment.Additionally or alternatively, the thresholds T₁, T₂, T₃ may beexperimentally determined.

The steps of the method 40 may be performed repeatedly, in anembodiment, to assess whether liquid is present and whether the sensor16 is functioning properly on an ongoing basis. That is, a continuousloop of driving the light source 20, receiving light with the lightdetector 22, and comparing the amount or intensity of light received toone or more thresholds may be executed. In an embodiment in which thefirst, second, and third driving steps 42, 48, 58 utilize the samefrequency and intensity of light, the light source 20 may becontinuously driven at a single frequency and intensity.

In an alternate embodiment, the third driving, receiving, and comparingsteps 58, 60, 62 may be omitted and, if the first amount of receivedlight R₁ is greater than the first threshold R₂, it may be concludedthat no liquid is present.

The first driving, receiving, and comparing steps 42, 44, 46 may beconsidered steps in an embodiment of a method of assessing the presenceof liquid (i.e., a liquid detection mode). The second and third driving,receiving, and comparing steps 48, 50, 52, 58, 60, 62 may be consideredsteps in an embodiment of a method of assessing the operational state ofthe sensor (i.e., a testing mode). The liquid presence assessment methodmay be performed separately and independently from the operational stateassessment method, in an embodiment. For example, the operational stateassessment method steps 48, 50, 52, 58, 60, 62 may be performed on aless-frequent basis than the liquid presence assessment steps 42, 44,46, in an embodiment. Furthermore, although the method 40 is illustratedand described such that the operational state assessment steps 48, 50,52, 58, 60, 62 are only performed after performing the liquid presenceassessment steps 42, 44, 46, such description and illustration isexemplary only. In an embodiment, the operational state assessment steps48, 50, 52, 58, 60, 62 may be performed regardless of performance of theliquid presence assessment steps 42, 44, 46.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and various modifications andvariations are possible in light of the above teaching. The embodimentswere chosen and described in order to explain the principles of theinvention and its practical application, to thereby enable othersskilled in the art to utilize the invention and various embodiments withvarious modifications as are suited to the particular use contemplated.It is intended that the scope of the invention be defined by the claimsand their equivalents.

What is claimed:
 1. A method of operating a sensor to assess thepresence of liquid, the method comprising: driving first light with alight source of the sensor at a first intensity; receiving reflectedfirst light with a light detector of the sensor; comparing an amount orintensity of first light received to a first threshold; driving secondlight with the light source at a second intensity; receiving reflectedsecond light with the light detector; comparing an amount or intensityof second light received to a second threshold; and concluding whetherliquid is present between the light source and the light sensor andwhether the sensor is functioning properly according to the result ofthe comparing steps.
 2. The method of claim 1, wherein the intensity ofthe second light is equal to the intensity of the first light.
 3. Themethod of claim 1, wherein the intensity of the second light is selectedaccording to a result of comparing an amount or intensity of first lightreceived to a first threshold.
 4. The method of claim 1, wherein theintensity of the second light is greater than the intensity of the firstlight.
 5. The method of claim 3, wherein the intensity of second lightis high enough to propagate through an expected liquid.
 6. The method ofclaim 1, wherein concluding comprises concluding that the sensor is notfunctioning properly if the amount or intensity of received second lightis not greater than the second threshold and concluding that liquid ispresent between the light source and the light detector if the amount orintensity of received second light is greater than the second threshold.7. The method of claim 1, wherein the second threshold is set higherthan the amount or intensity of light that a normally-functioning sensorcould detect given the intensity of the second light.
 8. The method ofclaim 1, wherein concluding comprises concluding that the sensor is notfunctioning properly if the amount or intensity of received second lightis greater than the second threshold and concluding that liquid is notpresent between the light source and the light detector if the amount orintensity of received second light is not greater than the secondthreshold.
 9. The method of claim 1, wherein the frequency of the firstlight is the same as the frequency of the second light.
 10. The methodof claim 1, wherein the first light and the second light are in theinfrared or near-infrared portion of the electromagnetic spectrum. 11.The method of claim 1, wherein the first intensity and the secondintensity are selected at least partially based on properties of anexpected liquid.